Notice that this problem can be solved using prefix sum arrays.

The brands denotated with a ~0~ will cause a change of -1, and the brands denotated with a ~1~ will cause a change of 1. If the prefix sum array, ~a~, has the same value at indexes ~i~ and ~j~, meaning that ~a_{i} = a_{j}~, then the number of ~+1~s that occur in [i, j - 1] must be equal to the number of ~-1~s.

The index of the last element with the value ~a_i~, should be stored to answer the queries. Each query can be answered by the difference between the index given and the index of the last element with the same ~a_i~ value. Note that if an index array is used to store these values, the values in the prefix sum array cannot be negative. Starting the PSA with an initial value of ~10^5~ suffices.